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| author |   Eric Dumazet <eric.dumazet@gmail.com> | 2011-03-28 18:06:58 +0200 |
|---|---|---|
| committer |   Tejun Heo <tj@kernel.org> | 2011-03-28 18:06:58 +0200 |
| commit | 5f55924deaa62d6df687c131fb92aebe071ec787 (patch) | |
| tree | 2888f5163793d9b37ff6726e470853d5d727abe3 /arch/x86/include/asm/percpu.h | |
| parent | percpu: Cast away printk format warning (diff) | |
| download | linux-dev-5f55924deaa62d6df687c131fb92aebe071ec787.tar.xz linux-dev-5f55924deaa62d6df687c131fb92aebe071ec787.zip | |
percpu: Avoid extra NOP in percpu_cmpxchg16b_double
percpu_cmpxchg16b_double() uses alternative_io() and looks like :
e8 .. .. .. .. call this_cpu_cmpxchg16b_emu
X bytes NOPX
or, once patched (if cpu supports native instruction) on SMP build :
65 48 0f c7 0e cmpxchg16b %gs:(%rsi)
0f 94 c0 sete %al
on !SMP build :
48 0f c7 0e cmpxchg16b (%rsi)
0f 94 c0 sete %al
Therefore, NOPX should be :
P6_NOP3 on SMP
P6_NOP2 on !SMP
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/percpu.h')
| -rw-r--r-- | arch/x86/include/asm/percpu.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index d475b4398d8b..d68fca61ad91 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -509,6 +509,11 @@ do { \ * it in software. The address used in the cmpxchg16 instruction must be * aligned to a 16 byte boundary. */ +#ifdef CONFIG_SMP +#define CMPXCHG16B_EMU_CALL "call this_cpu_cmpxchg16b_emu\n\t" P6_NOP3 +#else +#define CMPXCHG16B_EMU_CALL "call this_cpu_cmpxchg16b_emu\n\t" P6_NOP2 +#endif #define percpu_cmpxchg16b_double(pcp1, o1, o2, n1, n2) \ ({ \ char __ret; \ @@ -517,7 +522,7 @@ do { \ typeof(o2) __o2 = o2; \ typeof(o2) __n2 = n2; \ typeof(o2) __dummy; \ - alternative_io("call this_cpu_cmpxchg16b_emu\n\t" P6_NOP4, \ + alternative_io(CMPXCHG16B_EMU_CALL, \ "cmpxchg16b " __percpu_prefix "(%%rsi)\n\tsetz %0\n\t", \ X86_FEATURE_CX16, \ ASM_OUTPUT2("=a"(__ret), "=d"(__dummy)), \ |